Discovery of Grass Carp Larvae in the Colorado River Arm of Lake Powell

Abstract

Grass Carp Ctenopharyngodon idella stocking in the upper Colorado River basin is statutorily limited to triploid, i.e., functionally sterile, individuals. Systematic fish sampling in the upper Colorado River basin indicates adult Grass Carp remain rare but have been increasing in abundance since 2007. Grass Carp larvae collected in the Colorado River arm of Lake Powell, about 26 km downstream from the inflow, in 2015 and 2016, are evidence of the presence of a spawning population. These larvae were the first documentation of Grass Carp spawning in a river basin of the western United States. While Grass Carp reproductive biology suggests spawning occurred in the Colorado River or its tributaries upstream from Lake Powell, the sample location, age, and number of larvae collected pose the possibility of reservoir spawning. Addition of another, reproductively viable, nonnative, fish species to the already heavily invaded upper Colorado River basin could further impact conservation of the federally endangered native fishes.

A Review of Grass Carp and Related Species Literature on Diet, Behavior, Toxicology, and Physiology Focused on Informing Development of Controls for Invasive Grass Carp Populations in North America

“…In trials assessing the effect of five different light colors on the efficacy of a fish capture system for juvenile grass carp, capture rate is highest for blue light, second highest for natural light, third highest for green light, fourth highest for white light, and lowest for red light [459]. The successful use of WaterMark Quadrafoil (Jackson, Mississippi) larval fish light traps set overnight to collect grass carp larvae was documented by [460]. Silver and bighead carp visual sensitivity is temporarily depressed by strobe lights, making optical barriers less effective for deterring these fishes [461].…”

Policy Challenges Relating to Integrated Pest Management of Freshwater Aquatic Invasive Animals

“…For example, it is legal to transport, sell, and stock diploid Grass Carp Ctenopharyngodon idella in seven states (Alabama, Mississippi, Arkansas, Missouri, Iowa, Nebraska, and Hawaii) and the eastern half of Colorado, whereas the use of Grass Carp in surrounding states is either prohibited or restricted to sterile triploid fish (Stuewe 2014). Under these differing state-by-state management approaches, there is a continued risk of range expansion by Grass Carp (Brandenburg et al 2019). A national, integrated policy will require that all states POLICY CHALLENGES FOR INTEGRATED PEST MANAGEMENT adopt consistent and complementary regulations (MICRA 2015), particularly in the absence of national interstate prohibitions.…”

“…Under these differing state‐by‐state management approaches, there is a continued risk of range expansion by Grass Carp (Brandenburg et al. 2019). A national, integrated policy will require that all states adopt consistent and complementary regulations (MICRA 2015), particularly in the absence of national interstate prohibitions.…”

Introduction to a Special Section: Integrated Pest Management—Extending a Terrestrial Paradigm to Aquatic Environments

“…Since escaping containment, all of these species have established reproducing populations in the Mississippi River basin. Grass Carp are also reproducing in two Lake Erie tributaries (Embke et al 2016;USGS 2019) and in the upper Colorado River basin (Brandenburg et al 2019). The rapid spread of Bighead Carp and Silver Carp since the early 1990s has resulted in their becoming the most abundant species in terms of biomass throughout much of the Mississippi and Illinois rivers (e.g., Irons et al 2007) and causing declines in native planktivores (Irons et al 2007).…”

“…2016; USGS 2019) and in the upper Colorado River basin (Brandenburg et al. 2019). The rapid spread of Bighead Carp and Silver Carp since the early 1990s has resulted in their becoming the most abundant species in terms of biomass throughout much of the Mississippi and Illinois rivers (e.g., Irons et al.…”